Interface Engineering Enables Stable Aqueous Ammonium-Ion Batteries

The development of aqueous ammonium-ion batteries (AAIBs) is constrained by the scarcity of robust anode materials. MoO 3 , featuring large ionic migration channels and high theoretical capacity, has been extensively studied as a potential host anode material for the reversible intercalation and deintercalation of NH 4 + . However, the sluggish ionic migration kinetics, structural degradation caused by the stress of large-sized NH 4 + ions, and chemical corrosion in the electrolytes lead to dramatic capacity fading and short lifespan of MoO 3 . Herein, we propose an interphase engineering approach to simultaneously achieve high capacity and excellent cycling stability for AAIBs by employing a concentrated 24 m NH 4 CF 3 SO 3 electrolyte to construct a stable solid electrolyte interface that inhibits parasitic reactions and dissolution. The strategy endows the MoO 3 anode with remarkable cyclability, retaining 73.6% of its initial capacity after 500 cycles at 25 A g −1 . When evaluated in full-cell configurations, our approach achieves high energy density of 80.8 Wh kg −1 and outstanding durability, with 64.1% capacity retention over 4000 cycles at 20 A g −1 . This work offers valuable insights into the design of interface chemistry for high-performance AAIBs.